The present invention relates to a stepless speed change gear.
Until now, many devices of various constructions have been developed to convert rotary motion into linear reciprocating motion. The typical one is a crank chain. The crank chain has such a contruction that a crank is mounted on a rotating shaft, and a crank rod is connected to a reciprocating motion part, for example, a piston.
However, in the case of a crank chain, the relation between crank angle and the amount of the displacement of a piston is represented by sine curve, as shown by the broken line in FIG. 1a, while speed change ratio of the piston with regard to time is represented by a cosine curve, as shown by the broken line in FIG. 1b. Therefore the piston does not show uniform motion during its linear motion in one direction.
On the other hand, many devices of various constructions have also been conceived in which a rocking rod whose one end is pivotally supported is put in rocking motion around its fulcrum as a center, and such rocking motion is transmitted to a rotating shaft to reciprocate it. However, in the case of the above-mentioned devices, when the rocking angle of the rocking rod is constant, the rotating angle of reciprocating rotary motion of the rotating shaft is usually apt to be uniform. For this reason, a very complicated construction is required to adjust the above-mentioned rotating angle. Meantime, various constructions have been devised as means to convert reciprocating rotary motion into unidirectional rotary motion. A well known example is one way clutch using a ratchet mechanism. However, most of the conventional one way clutches transmit the power of the reciprocating rotary shaft to an output shaft only during rotating motion without using the power of the above shaft during its returning rotating motion. Therefore, the conventional devices of this kind have very low power transmission efficiency.